1. Field of the Invention
This invention relates to a multiple conductor fluid handling duct for an automotive vehicle.
2. Disclosure Information
Automotive vehicles typically include equipment for air conditioning and heating their passenger compartments. Air conditioning systems usually comprise an engine driven compressor having one or more evaporator cores coupled thereto and associated duct work for conducting air past the evaporator core so as to chill and dehumidify the air. In similar fashion, heating systems utilize a heater core through which engine coolant passes as part of an accompanying ducting system. Air conditioning and heating duct work may be either combined or separated depending upon the design of the particular system. Another feature which may be incorporated is that of a fresh air inlet capable of mixing outside air with either the heated or chilled air, as desired by the vehicle operator. Early examples of fluid handling duct work for automotive vehicles are shown in U.S. Pat. Nos. 2,301,512 and 2,651,986.
The concept of a divided flow duct is shown generally in U .S. Pat. No. 2,902,838 in which a refrigerated fluid chills air which can selectively be passed through a cold storage compartment or to a register and into the passenger compartment.
The designers of air conditioning systems have used several types of channel means for ducting conditioned air about the interior of automobile passenger compartments. For example, U.S. Pat. No. 3,456,572 discloses a dash panel assembly including a rigid panel having a resilient crash padding mounted over its surface and defining a single fluid channel circumscribed by the padding, a rigid portion of the structure and further by foam insulation incorporated therein.
U.S. Pat. Nos. 4,391,465 and 4,559,868 disclose multiple channel air handling ducts. Although each of these designs provides means for conducting fluid through more than one channel through the duct, each suffers from a common disadvantage inasmuch as the components of the duct are joined at least in part by bolted or riveted fasteners. This joining method may be expected to cause problems during the production process because fasteners are sometimes not properly set or, indeed, sometime are not provided at all in their appropriate locations; as a result the duct work will not be joined properly. This deficiency imposes a serious problem because the fluid intended to be conducted through the duct may be lost. Of equal importance is the fact that the improperly joined duct will give rise to squeaks and rattles audible by the passengers. This may be preceived as a serious quality control problem.
A method for joining plastic subassemblies or components into a finished fluid handling duct could use known techniques of ultrasonic and friction welding, examples of which are shown in U.S. Pat. Nos. 3,002,871, 4,305,988; and 4,333,978. A further example of a friction welding process for use with a thermoplastic container is disclosed in Japanese patent 41/16,276. Friction welding is commonly performed by clamping two flat thermoplastic sheets and then reciprocating one sheet with respect to the other. This causes the contacting sheets to rub and to become heated by friction so that the contacting faces melt. These molten areas rigidify and weld when the reciprocation is stopped and the sheets cool. A more detailed explanation of one friction welding technique suitable for closing a channel is included in U.S. Pat. No. 4,377,428, which is incorporated by reference herein.
Two examples of divided channels are disclosed in British patent No. 969,959 and in German Offenlegungsschrift No. 2,319,992. Unlike the fluid handling duct of the present invention, these patents disclose unitary ducts having interior and exterior walls either molded without seams or from a single piece of material which is worked into a multi section duct and then welded in one or more locations.